Answer
C, A, B, D. In this solution, we assume that "least" means "most negative" and "most" means "most positive".
Work Step by Step
The net forces in the four situations are, from left to right:
$$5 N - 10 N = -5N$$
$$3 N - 7 N = -4N$$
$$4 N - 12 N = -8N$$
$$3 N - 3 N = 0N$$
